Cataulacus tardus was found nesting in the canopy of a secondary-forest tree, in sampling conducted in tree crowns, in Gamba, Gabon. It was anecdotally reported to subordinate at tuna baits. C. tardus has been shown to exhibit directed movement while in freefall that allows workers that fall or purposely detach from a tree to glide back and regain a hold on the same tree trunk. This gliding behavior is shared with numerous members of the tribe Cephalotini, and other genera as well. (Yanoviak et al. 2005, 2007, 2008)

Identification

A member of the huberi group. Santschi notes that Cataulacus schoutedeni is close to Cataulacus tardus, but is smaller, the (propodeal) spines relatively longer, the sculpture more feeble'. Variations of this form are usual and may be universal amongst species of the huberi group, and the only real difference separating the types of the two forms in the present species (apart from obvious size differences) is the presence of an angle separating the vertex from the occiput in tardus, absent from schoutedeni. As has been noted the occurrence of this angle is restricted to large workers of the species and no grounds remain for maintaining the two names as separate species. (Bolton 1974)

Biology

Much of the information concerning the biology of Cataulacus species is anecdotal and fragmentary. Arnold (1917) wrote a succinct general overview of Cataulacus biology that still remains quite informative. Arnold reports "all the species of this genus are tree-ants, usually forming medium sized nests in hollow twigs and stems, or more rarely, under the bark. They are timid and slow-moving insects, often feigning death or dropping rapidly to the ground when disturbed. As Bingham has remarked in connection with this genus (Fauna Brit. India, Formicidae), these ants have the habit of wandering over the trunks of trees and the leaves in what appears to be a very aimless and languid manner. I have occasionally seen them breaking open the earthen tunnels constructed by termites over the trunks of trees and attack the inmates."

Bolton (1974) expands upon this earlier account - "All known Cataulacus species are arboreal or subarboreal nesters and they predominantly forage on the trees and shrubs in which the nests are situated. Very few appear to come down to ground level but in West Africa the small species Cataulacus pygmaeus and Cataulacus brevisetosus may be found foraging in leaf litter or crossing the ground to ascend a tree other than the one in which the nest is situated. The nests themselves are usually constructed in small hollow twigs or stems by the smaller species and in rotten branches or rotted portions of the tree trunk by the larger species. This is rather a generalization as some small species are known which nest in and under rotten bark (e.g. Cataulacus vorticus) and undoubtedly some of the larger forms will eventually be found inhabiting relatively small cavities in plants.

On the plants ants of the genus Cataulacus often occur together with Oecophylla or species of Crematogaster, and appear to be mostly tolerated (at least they are not evicted) by the majority of these forms. Their defence against attackers of these genera lies primarily in their armoured exterior, but their ultimate escape reaction is to curl up and release their grip on the plant, falling to the ground and thus making their escape. The decision to remain immobile and present an armoured surface or to drop from the plant appears to depend upon the size or persistence of the aggressor; larger attackers usually precipitate the latter reaction, but it has also been noted as a result of persistent and unwanted attention by a series of workers of a small Crematogaster species.

The majority of species are forest-dwelling forms, with relatively few adapted to savannah or veldt conditions. Those which do, however, occur in these zones tend to be very successful in their chosen habitat and often possess a wide distribution. A few species are apparently able to exist in any region of
Africa providing the basic essentials of nesting-site and food supply are met with, but on the whole the fauna may be divided into forest and non-forest forms."

Some species have nests that can be protected by a single worker's head, as its shape matches the nest entrance and forms an effective plug.

Occipital margin usually without crest separating vertex from occiput, the two surfaces confluent; but in some large workers an acute angle separates the two surfaces. Occipital comers without teeth or denticles, rounded; the sides of the head behind the eyes often irregular but never denticulate. Margins of alitrunk not denticulate; the pronotum strongly marginate, the remainder not marginate, with the dorsum rounding evenly into the sides. Pronotal margination expanded laterally, subrectangular in shape, the edges straight or irregular and strongly converging posteriorly to the mesonotal surface. Promesonotal suture absent or represented in the largest workers by a very faint and extremely shallow arcuate impression. Propodeum with a pair of long, strong, acute spines, as long as or longer than the dorsal length of the petiole. First gastral tergite not marginate.

Dorsum of head extremely finely, densely and faintly reticulate-punctate, with a loose, very fine, scattered rugoreticulum. In some specimens the rugulation is effaced or nearly so over some areas of the cephalic dorsum. Dorsal alitrunk similarly sculptured but with the rugulae tending to assume a longitudinal direction. First gastral tergite predominantly or totally finely reticulate-punctate, but in some specimens a few very faint rugulae are visible.

Dorsal surfaces of head, alitrunk and gaster without hairs. Margins of head behind eyes and margins of alitrunk without hairs, or the former with one or two minute hairs which, however, do not project freely beyond the margin.